Processing of flexible substrates, such as plastic films or foils, is in high demand in the packaging industry, semiconductor industries and other industries. Processing may consist of coating of a flexible substrate with a desired material, such as a metal, in particular aluminum. Systems performing this task generally include a processing drum, e.g., a cylindrical roller, coupled to a processing system for transporting the substrate, and on which at least a portion of the substrate is processed. Roll-to-roll coating systems can, thereby, provide a high throughput system.
Typically, an evaporation process, such as a thermal evaporation process, can be utilized for depositing thin layers of metals which can be metallized onto flexible substrates. However, Roll-to-Roll deposition systems are also experiencing a strong increase in demand in the display industry and the photovoltaic (PV) industry. For example, touch panel elements, flexible displays, and flexible PV modules result in an increasing demand of depositing suitable layers in Roll-to-Roll coaters, particularly with low manufacturing costs. However, such devices typically have several layers, which are typically manufactured with CVD processes and particularly also PECVD processes.
The combination of several CVD, PECVD and/or PVD sources working with different gas mixtures and/or different working pressures faces the need of an excellent process gas separation to avoid cross contamination effects in the subsequent process steps and to ensure the long term process stability. Thereby, as compared to the state of the art, a gas separation level should beneficially be improved by at least a few orders of magnitude. Typically the deposition of complex thin film layer structures are performed subsequent in different R2R coaters, each one designed to the needs of the special deposition technique. However, this concept results in high costs of ownership (CoO) for the manufacturing equipment.
In some Roll-to-Roll coating machines, the compartments, e.g. sputter compartments, can be separated by a slit which follows the curvature of the coating drum. The gas separation is strongly dependent on the slit width between the coating drum and the gas separation unit and on the length of the slit. The optimal gas separation factor is achieved when the slit width is as small as possible. The slit width depends on the adjustment of the gas separation unit, the thickness of the plastic film and the temperature of the coating drum. Since the diameter of the coating drum increases with temperature, the gas separation slit is adjusted for the maximum specified coating drum temperature (e.g. 80° C.) and the maximum plastic film thickness (e.g. up to 500 micron). If thinner films and lower drum temperatures are to be processed with such a set-up, the only way to improve this situation is a new geometrical adjustment of the gas separation walls for the given process conditions. If this is done, the operator of the machine must be aware of the fact that under different process conditions, such as, with higher coating drum temperature, the diameter of the coating drum will expand and there is a chance that the separation walls will come into contact mechanically with the rotating coating drum. This results in a dramatic failure for the operator because the coating drum is scratched and a long and expensive re-work of the coating drum is unavoidable. Therefore, a gas separation adjustment for low coating temperatures is almost never done in real life.
OLED displays have gained significant interest recently in display applications in view of their faster response times, larger viewing angles, higher contrast, lighter weight, lower power, and amenability to flexible substrates, as compared to liquid crystal displays (LCD). In addition to organic materials used in OLEDs, many polymer materials are also developed for small molecule, flexible organic light emitting diode (FOLED) and polymer light emitting diode (PLED) displays. Many of these organic and polymer materials are flexible for the fabrication of complex, multi-layer devices on a range of substrates, making them ideal for various transparent multi-color display applications, such as thin flat panel displays (FPD), electrically pumped organic lasers, and organic optical amplifiers.
Over the years, layers in display devices have evolved into multiple layers with each layer serving a different function. Depositing multiple layers onto multiple substrates may require multiple processing chambers. Transferring multiple substrates through multiple processing chambers may decrease substrate throughput. Therefore, there is a need in the art for an efficient method and apparatus for processing such OLED structures and other modern more sophisticated devices to ensure substrate throughput is maximized and substrate transferring is decreased.